add fish config

fish/add-on.fish

@@ -1,4 +1,12 @@
+# 兼容性添加 PATH
+if functions -q fish_add_path
     fish_add_path ~/.flinty/bin
+else
+    # 针对 Fish < 3.2.0 的版本
+    if not contains "$HOME/.flinty/bin" $PATH
+        set -gx PATH "$HOME/.flinty/bin" $PATH
+    end
+end
 
 # 禁用 Fish 默认欢迎语
 set -g fish_greeting ""